The present invention generally relates to methods and apparatus for testing biological samples, and in particular, to systems for in vitro testing of body fluid samples for analytes, such as glucose.
The ability to monitor an analyte within a blood sample has greatly improved the diagnosis and treatment of diseases such as diabetes. For example, home monitors allow diabetics to test glucose levels by pricking their finger and applying a small sample of blood to a test strip. Based on the glucose reading, diet and/or insulin dosage can be adjusted.
Generally, these home glucose monitor systems use an electrochemical detection technique based on glucose oxidase reactions. The system can include a disposable strip having electrodes and the glucose oxidase enzyme. When a blood drop is applied to the target area of the electrode, the glucose oxidase catalyzes the oxidation of glucose in the drop to produce gluconic acid. During the reaction, electrons are transferred by an electrochemical mediator to the electrode surface. This in turn generates a current that is measured by the sensor. The amount of current generated is proportional to the amount of glucose present in the blood drop, thus giving an accurate reading of the blood glucose concentration.
While the ease of use and the low cost of these home monitor systems have proven helpful for regular blood sugar monitoring, they are limited by the amount of information that can be provided using a glucose oxidase reaction. Information on other substances within the blood is not readily available without incorporation of additional reagents and assays.
Spectroscopic approaches to glucose monitoring have also been suggested. In one such approach, laser light is directed through or into a portion of a patient's skin and reflectance or scattered light is captured by a detector. A spectroscopic measurement of the blood glucose level is then obtained from the detected light. This method has met with limited success because of the cost, complexity, and difficulty of transdermal monitoring.
For these reasons, there continues to exist a need in this art for better devices and methods for testing blood and other body fluid samples.